The present invention relates to a sheet-metal bending press.
Arrangements are known from the documents U.S. Pat. Nos. 4,356,716 and 4,836,004.
Document U.S. Pat. No. 4,356,716 describes and illustrates a bending press in which a C-shaped blade-holder is mounted for pivoting angularly by means of a rear arm, about an eccentric pin. The angular bending strokes are imparted to the blade-holder by one or more actuators which in turn are carried by an eccentric pin.
Adjustment of the angular position of the eccentric pin of the actuators enables the stroke of the blade-holder to be adjusted in a direction substantially perpendicular to the plane of the metal sheet, according to the degree of closure of the angle to be imparted to the bend; adjustment of the angular position of the eccentric pin on which the arm of the blade-holder is mounted moves the blade-holder towards or away from the blank-holder according to the thickness of the sheet metal to be bent and/or the angle to be given to the bend.
This known arrangement has the disadvantage of causing the blades to work in less than ideal conditions since, given the angular pivoting of the blade-holder, the working blade never remains parallel to itself during the bending operation as would, however, be desirable.
U.S. Pat. No. 4,836,004 describes and illustrates a bending press in which a C-shaped blade-holder body is mounted for sliding to and fro along an axis perpendicular to the plane of the metal sheet and its rear cooperates with a cam surface a central portion of which extends along the perpendicular axis and which has end portions curved towards the blank-holder. By virtue of this arrangement, the blade always works parallel to itself during the bending operation and moves towards the blank-holder towards the end of this operation to a greater or lesser extent according to the length of the stroke imparted along the axis perpendicular to the plane of the metal sheet. This permits the formation of bends with angles which are closed to a greater or lesser extent. However, since the cam surface cannot be modified except by the replacement of the entire cam, the ideal bending conditions corresponding to a given cam exist only for sheet metal of a particular thickness.